I couldn't come up with a short description for the title so here's the detailed one. If you deactivate a particle fountain (by either using Dormant flag, or Thing Deactivate linedef action, or Thing_Deactivate() ACS function) it stops producing particles and acts like if it's not there at all. This works correctly in singleplayer.

In online however, if the fountain was already deactivated by the time you connected to the server, your client does not get told of this and you see the fountain functioning (producing particles).

https://dl.dropboxusercontent.com/u/68200676/Doom/fountainbug.wad
Here's the tiny test map. The particle fountain has Dormant flag on it. If you run the map in singleplayer you will not see it initially (correct behaviour). The switch on the left will activate it and the switch on the right will deactivate it. Now run the map on the server and you will see it initially, as your client is not told about it being deactivated by Dormant flag. You can deactivate it with the switch on the right; it will be gone but if reconnect you will be seeing it once again.

EDIT: ...So I believe it does not send Z height of the fountains either. Might as well be other other thing options, I'm not sure yet. I'm starting to believe it's more of a feature request rather than a bug report..

Last edited by Sr69Mm-jC on Fri Aug 23, 2013 10:55 pm; edited 1 time in total

Ambient sounds have similar issue. If you deactivate an ambient sound, it does not play its sound any longer until activated again. Works fine in singleplayer but online the client is not informed about the deactivated state upon connect. Even worse, when the sound is activated, the sound plays twice from the ambient sound thing after it has been activated.

Example is TEH BASE map01, polyobj crusher alarm after the big hangar with 2 airplanes (crusher activates after pressing switch in the dark room after crusher).